Protective film formation by amoxicillin on nickel surfaces in acidic and alkaline corrosive media: Electrochemical and surface characterization with energy storage assessment

Background Nickel has wide applications in medical fields, such as surgical instruments, due to its strength and corrosion resistance. Amoxicillin has been tested as a corrosion inhibitor of Ni in acidic and alkaline environments. Amoxicillin contains heteroatoms (N, S, O) with lone pairs of electrons or π bonds. This enables it to adsorb chemically on the metal surface via the Langmuir isotherm. This protects the metal from corrosion. The novelty of the recent study lies in the corrosion protection of Ni in acidic and alkaline media, with comparisons and confirmation using two morphological techniques. Also, studies on the effects of temperature and adsorption mechanisms have been conducted in both acidic and alkaline media. In addition, energy storage studies are carried out in detail. The most important outcomes are presented in the charge-discharge section, including discharge time, specific capacitance, energy, and power variation over cycle number. Methods In this study, 0.5 M H₂SO₄ was used to examine the corrosion of Ni in the absence and presence of varying amounts of amoxicillin. Electrochemical measurements using Tafel polarization curves and impedance spectroscopy showed a decrease in corrosion current density (icorr) and an increase in inhibition efficiency with increasing concentration, reaching a maximum of 95% at 1 × 10⁻⁴ M at 55 °C. Both anodic and cathodic reactions were inhibited, and NiO formation was minimized. Temperature analysis showed that adsorption is exothermic and chemical in nature, as supported by the activation energy and thermodynamic values (ΔH 0 ads and Δ S 0 ads ). Significant Findings Charge-discharge test results showed improved capacitance (0.140 mA h r -1 in 0.1 M KOH + 1 × 10 –5 M amoxicillin and 0.634 mA hr -1 in 0.5 M H 2 SO 4 + 5 × 10 –4 M Amoxicillin). SEM analysis showed the formation of a smoother oxide film on Ni surfaces after the reaction. DFT calculations showed a lower Δ E gap for amoxicillin, indicating its ability for strong chemical adsorption and thus good inhibition efficiency. The expired amoxicillin antibiotic serves as an eco-friendly, efficient inhibitor that significantly improves the corrosion resistance and electrochemical properties of Ni in both acidic and basic solutions.